In recent years a need has arisen for filters, valves and occlusive devices that may be implanted percutaneously and transluminally. Such devices may be used either to filter particulate matter from a fluid flow, to regulate the fluid flow, or to partially or completely occlude the flow.
A number of devices are known for trapping particulate matter downstream of the site of a therapeutic procedure, e.g., angioplasty, to reduce embolization of materials following completion of the procedure. U.S. Pat. No. 4,723,549 to Wholey et al. describes a filter basket disposed from an angioplasty device to collect and trap frangible material liberated during an angioplasty procedure. U.S. Pat. No. 4,425,908 describes an implantable self-expanding filter basket formed of a plurality of nickel-titanium wires.
A number of devices also are known for occluding flow through a vessel. For example, U.S. Pat. No. 5,382,261 to Palmaz is directed to a deformable slotted stent that includes a membrane disposed transverse to the flow direction to occlude the vessel. These devices may be advantageously used wherever it is desired to occlude flow, for example, through a arterio-venous fistula, or as part of the treatment of a congenital heart defect.
A number of devices also are known for regulating the flow of tissue through a body vessel or organ. U.S. Pat. No. 5,655,548 to Nelson et al. describes a tubular member including a valved portion for regulating the flow through an arterio-venous passageway. U.S. Pat. No. 5,409,019 to Wilk describes regulating flow through a myocardial passageway using a first embodiment comprising a multi-part rigid stent that includes valve flaps, and an alternative embodiment wherein the stent itself is biased to collapse during cardiac diastole.
A drawback of the foregoing devices is that they generally are not compatible with previously known delivery devices, and require special handling for optimum performance. In addition, such devices have a limited range of applications in which they may be employed. Specifically, the ability to deliver such devices to small diameter vessels depends on the specific configuration of the device and its intended purpose.
A stent design particularly well suited for use as a base for a filter, valve or occluder is the coiled sheet stent of the type described in U.S. Pat. No. 5,007,926 to Derbyshire, and U.S. Pat. No. 5,443,500 to Sigwart, which are incorporated herein by reference. A coiled sheet stent generally comprises a flat relatively flexible mesh, and may have teeth on one edge and openings that accept the teeth on the opposing edge. The stent is formed by rolling the mesh into a tube, with the edge oriented inside and aligned with the axis of the tube. The stent generally is formed of a resilient material, such as stainless steel or a nickel-titanium alloy, and may be designed to be highly crush resistant.
The foregoing coiled sheet stents may be percutaneously and transluminally delivered by rolling the stent to a small diameter and inserting it into a sheath that retains the stent in the contracted state. Such a delivery system is described in U.S. Pat. No. 4,665,918 to Garza et al., which is also incorporated herein by reference. Upon delivery of a coiled sheet stent to the implantation site, the constraint (e.g., sheath) is removed, and the stent is permitted to unroll. The stent may be further expanded into position using a conventional balloon dilatation device, thereby locking the teeth into engagement with the openings in the opposing edge.
In view of the foregoing, it would be desirable to provide apparatus that may be delivered using previously known delivery apparatus, and that can be delivered to small vessels and through tortuous vessel anatomy.
It further would be desirable to provide a device capable of being employed as either a filter, a valve or occluder, depending upon the desired therapeutic application.
It also would be desirable to provide a device capable of being employed in filter, valve or occluder applications that builds upon the acknowledged advantages of coiled sheet stent technology, including capability to achieve very small delivery diameters, ease of deployment, high crush resistance, and low migration potential.